Colloquium
Infrared spectropolarimetry of a C-class solar flare footpoint plasma
Abstract
We performed full Stokes spectropolarimetric observations of loop footpoints in the active region NOAA 13363 during a C-class flare with the GREGOR Infrared Spectrograph (GRIS) on 2023 July 16. The observed spectral region included the photospheric Si I 10 827 A and Ca I 10 839 A lines and the chromospheric He I 10 830 A triplet. Simultaneously, high-cadence and high-resolution imaging observations were carried out with the improved High-resolution Fast Imager (HiFI+) in the Ca II H line and TiO bands. The observations were conducted under excellent seeing conditions, as confirmed by the Fried-parameter measurements. Speckle-restored HiFI+ Ca II H images revealed thin flare-related filaments and diffuse haze-like emissions, further confirmed by background-subtracted solar activity maps (BaSAMs), which localized chromospheric variability near the sunspot. The He I triplet showed enhanced emission during the flare events and developed intense red- and blue-shifted components, with the decisive shift of 90 km/s, suggesting the significant energy release and plasma motion triggered by the flare. Simultaneously, a delayed increase in the Si I line wing intensity was observed approximately 6 minutes after the He I emission, suggesting that the upper photosphere experienced secondary heating, possibly due to thermal conduction rather than energetic particles. This time delay and spatial correlation support a scenario where dynamic flare processes influence chromospheric and upper photospheric layers. Our results demonstrate a temporal and spatial coupling between chromospheric and upper photospheric regions, and the time delay rules out direct heating by flare-accelerated electrons, so we propose thermal conduction or ionization effects as possible mechanisms.
About the talk
Astronomical Institute Slovak Academy of Science
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About the speaker
Dr. Zurab Vashalomidze is a physicist specializing in solar physics and space weather. He earned his Ph.D. in physics from Ilia State University, Georgia, where he was also honored in 2016 with the Pascal Prize awarded by Ilia State University in recognition of his outstanding academic achievements. He subsequently held a postdoctoral position at the Astronomical Institute of the Slovak Academy of Sciences.
His research interests include the dynamics and evolution of chromospheric jets (spicules), radiative transfer modeling of prominences, and detailed investigations of coronal rain, encompassing its appearance, velocity, and acceleration. In recognition of his contributions as an early-career scientist, Dr. Vashalomidze received the Young Scientist Award named after Mikheil Vashakidze from the Evgeni Kharadze National Astrophysical Observatory of Georgia.
As a young researcher, he was also awarded a two-year fellowship under the “Fellowships for Excellent Researchers R2-R4” program (09I03-03-V04-00015) supported by the Office of the Government of the Slovak Republic. Dr. Vashalomidze has actively participated in several national and international projects, including one domestic project under “SK-PL Open Mobility” and two research initiatives funded by the Shota Rustaveli Georgian National Science Foundation. He contributed as a key researcher to the international Solar and Space Weather Network of Excellence (SOLSPANET FP7-PEOPLE-2010-IRSES-269299) and successfully completed a doctoral research grant (PHDF2016-147) from the same foundation.
In 2023, as Principal Investigator (PI), he secured observing time on the GREGOR solar telescope in Tenerife (Canary Islands) through the European Union’s Horizon 2020 research and innovation program (SOLARNET, grant agreement No. 824135). That same year, he also participated in an observing campaign at the Swedish Solar Telescope (SST) in La Palma (Canary Islands). In 2025, as Co-PI, he took part in an on-site ground-based observing campaign at the Goode Solar Telescope (GST) in Big Bear Lake, California, USA. Additionally, in 2018 he participated in an earlier observing campaign at the SST.
Dr. Vashalomidze is highly motivated to continue advancing his career in the complex study of the solar corona using both ground-based and space-based instruments. He has extensive experience with data acquisition and processing from spacecraft observations, and thorough expertise in the computational tools required for such analyses.